The present invention relates generally to dental implant systems and methods for replacing missing teeth with dental implants, more particularly, to dental implant systems and surgical methods for replacing teeth with dental implants in areas of the mouth that have suffered bone loss and most particularly to combination distraction dental implant devices and methods for replacing missing teeth in areas of the jaw bone having bone loss using a three component combination distraction dental implant device including two cylindrical like components and a connecting third component or an expansion third component to grow new bone and soft tissue by distraction osteogenesis.
Premature tooth loss can limit a patient's ability to chew and speak clearly. Consequently, patients request tooth replacement. In the past, dentists have been able to replace missing teeth by means of removable prosthesis such as partial or complete dentures. Other prior alternatives included the placement of fixed bridge work cemented to adjacent teeth. These two prior methods served only to fill the void of the edentulous space by replacing the crown of the involved teeth but did not replace the root.
Recently, the field of dental implantology has come into its own, as the technology for replacement of the root and the crown portion of the missing teeth has evolved. In dental implantology, the root portion of the missing tooth is replaced first, by surgically implanting a cylindrical root form dental implant into the dentoalveolar bone (Stage I). There are a number of U.S. Patents relating to dental implants, including the following: U.S. Pat. Nos. 5,489,210; 5,470,230; 5,449,291; 5,334,024; 5,281,140; 5,269,685; 5,259,759; 5,154,612; 5,145,371; 5,125,841; 5,069,622; 5,064,425; 5,051,880; 4,960,381; 4,824,372; 4,798,205; 4,682,951; 4,657,510; 4,552,532 and 4,330,891 the disclosure of each is herein incorporated by reference.
As the surgical site heals, the dental implant becomes bonded and incorporated into the surrounding bone forming an integral unit. The dental implant abutment for the creation of the crown of the tooth later, once osseous healing had occurred (4-6 months), is placed at the time of Stage II uncovering.
In some instances, the above is accomplished by a one-stage implant procedure. In the one-stage procedure, also known as the nonsubmerged, either a one-piece fixture, in which the implant and transmucosal portion are fused together, or both an implant body and a healing cap are simultaneously placed. Instead of covering the implant, the soft tissue is sutured around the protruding transmucosal portion or healing cap and left to heal for the same 4 to 6 months. The advantages of one-stage implants is described in detail in an article by Louis F. Clarizio, DDS, entitled "One-stage Implants: An Overview of Their Usefulness and the Techniques for Placement" in the Postgraduate Dentistry Series, Volume 3, Number 4, 1996 beginning at page 3, the disclosure of which is hereby incorporated by reference.
Regardless of whether a one-stage or a two-stage implant is used, long term success of dental implants depends upon two factors: (1) the osseous incorporation or integration of the implant with the native bone, and (2) the mechanical loading properties of the prosthetic crown onto the dental implant. Ideally, the longest (13-15 mm) and widest (2.5-5.5 mm) dental implant should be placed in the bone to act as a proper foundation for the tooth crown.
However, as a consequence of premature tooth loss, patients have lost bone in the area of a proposed implant. This bone loss has, in some cases, limited the surgical options, requiring the dentist to place a smaller than optimal sized dental implant. If the dental implant is too small to accommodate the mechanical load from chewing, with time, it will loosen and fail. Thus, the longest and widest implant available, as described above, (based on the bone stock) should be placed. Additionally, due to bone loss or insufficient bone in the implant area, the dental implant may be placed in an anatomical location where the existing bone may not be ideal for prosthetic reconstruction with a crown or bridge, forcing the dentist to replace the missing tooth with a crown that is not as aesthetic or functional as would be considered optimal.
One prior solution to this bone loss problem was to augment the bony bed with the patient's own bone or cadaveric bone as a transplant, or with synthetic bone substitutes. This procedure was done at the time of dental implant placement if the bone loss is not too great. Otherwise the bone augmentation must be done as a first surgical procedure with the placement of the dental implant occurring several months later, as a second surgical procedure, once healing of the bone graft was completed.
Due to the anatomy of the craniofacial region (defined as pertaining to the region of the head which contains the craniofacial bones, including the maxilla, the upper jaw bone includes the bones of the eyes, the hard palate and the nose, and the mandible, the lower jaw bone, usually with reference to specialized surgical or prosthetic reconstructions of this area of the face), augmentation of the deficient bone is not as simple as layering on the transplanted bone and allowing it to heal. Occasionally, the maxillary sinus membrane (located in the upper jaw) must be elevated or the inferior alveolar nerve (located in the lower jaw) transposed to allow room for placement of the bone graft. Regardless of the technique and materials used, the potential morbidity to the patient can be significant.
Another prior technique of producing new bone was that of distraction osteogenesis. Here, the body was "tricked" into making new bone as it attempts to heal a fracture site. Using this technique, the surgeon created an osteotomy or cut in the bone in an area of bone deficiency. As long as a non-critical size gap exists, the body attempts to heal itself by filling in the gap with new bone. If the gap is widened daily, the body recognizes the newly expanded gap and continues to fill the gap with new bone. This results in creation of new bone in the expansion gap. As long as the gap is expanded slowly over time (0.5-2.0 millimeters per day), the body continues to heal the gap, generating new bone.
A critical size defect is one that will not heal on its own i.e. a critical size defect is sufficiently large to allow only for connective tissue healing without bone bridging between the two ends of the defect. A non critical defect is one which will heal on its own by filling in with bone. Each bone of the body has its own "critical size" defect. If a critical size defect exists, then a bone graft or a bone substitute must be placed to allow for osseous regeneration.
Since the native bone is utilized as the template for repair, the new bone generated has the same size and shape as the original bone. This phenomenon of recreating the same size and shape as the original bone is unique to bone generation using distraction osteogenesis and is not accomplished with conventional bone transplantation.
During distraction osteogenesis, in addition to creating new bone, the overlying soft tissues are regenerated, a secondary gain unique to distraction osteogenesis. This secondary beneficial effect has significant clinical implications, for not only is the underlying foundation properly established, but also the overlying soft tissue is recreated providing for aesthetic and functional rehabilitation of the defect.
Distraction osteogenesis defined as the generation of new bone in response to the application of tension stresses placed across an osteotomy site (bone cut site), has been successfully applied to the bones of the maxillofacial region and specifically to the dentoalveolar unit using distraction devices that are external to at least the gums inside the mouth and, in some cases, completely external the mouth. In these prior instances of applying distraction osteogenesis prior to placing a dental implant, an osteotomy (corticotomy) is made in the bone adjacent to the area requiring bone augmentation and one of the prior bone expansion devices was applied. After allowing for a period of initial healing, the prior device was activated by the patient at home, advancing the distraction gap about 0.5 to about 2.0 millimeters a day. For a more complete description of distraction osteogenesis, see the article "Osteodistraction" by the inventor of the present application in Selected Readings in Oral and Maxillofacial Surgery, volume 4, Number 7, published by the University of Texas, Southwestern Medical Center at Dallas, in 1996, the disclosure of which is herein incorporated by reference.
After a sufficient amount of new bone matrix was generated, the distraction device was left in place to allow for ossification of the newly generated bone. The prior distraction devices were then removed during a second surgical procedure and dental implant(s) are placed. Once again the patient was required to undergo two surgical procedures: (1) bone generation via distraction osteogenesis and (2) placement of the dental implant.
A minimum of about ten (10) to about fifteen (15) millimeters of bone was required to utilize the existing distraction devices. If there was not enough bone stock to place the existing devices, a bone graft was required prior to the distraction device being placed. In this case, the patient was required to undergo three separate surgical procedures.
The current external and submerged distraction devices are also limited in the amount of bone expansion each device can deliver because they have fixed internal mechanisms which provide for bone expansion from 0.0 mm to the full length specified for a particular device. Presently, for an external distraction device the full length is about 40 mm while for an intraoral distraction device, the full length is about 18 to about 20 mm. Should more bone expansion be required, then a new device was required to be placed during yet another surgical procedure (fourth).
These prior distraction devices took essentially two approaches: (1) the device was situated externally, outside the skin, with pins holding the device in place to the bone, or (2) the device was situated intraorally, inside the mouth, along the gum line, with pins or screws holding the device in place. Devices which are located externally function well but can pose aesthetic concerns while the patient is utilizing the device and also facial scars are created as the pins holding the device in place are moved as the device is activated and the bone is expanded. Intraoral devices do not have as many aesthetic concerns, but are bulky, displacing the lips and cheeks, which can give the patient the appearance of a local infection.
As can be seen above, in the worst case, some patients were required to undergo as many as four (4) separate surgical procedures over a lengthy time period in order to achieve an optimal dental implant. It should be obvious that it is desirable to limit the number of surgical procedure a patient must undergo.
Thus, there is a need for new devices and methods for placing optimally sized dental implants in areas having insufficient bone. Such new devices and methods should reduce the number of surgical procedures a patient must undergo to achieve an optimal implant; should significantly reduce the number of individual distraction devices required for obtaining the appropriate amount of bone in the implant site; should reduce the number of surgical procedures required for placing an optimal implant in the implant site; should incorporate as many features of the prior devices as possible into a combination distraction dental implant device; should reduce patients aesthetic concerns; should reduce, if not totally eliminate, displaced lips and cheeks and should reduce, if not totally eliminate, the need for bone grafts.